Jump to content


Welcome to Ultimate Subaru Message Board, my lurker friend!

Welcome to Ultimate Subaru Message Board, an unparalleled Subaru community full of the greatest Subaru gurus and modders on the planet! We offer technical information and discussion about all things Subaru, the best and most popular all wheel drive vehicles ever created.

We offer all this information for free to everyone, even lurkers like you! All we ask in return is that you sign up and give back some of what you get out - without our awesome registered users none of this would be possible! Plus, you get way more great stuff as a member! Lurk to lose, participate to WIN*!
  • Say hello and join the conversation
  • Subscribe to topics and forums to get automatic updates
  • Get your own profile and make new friends
  • Classifieds with all sorts of Subaru goodies
  • Photo hosting in our gallery
  • Meet other cool people with cool cars
Seriously, what are you waiting for? Make your life more fulfilling and join today! You and your Subaru won't regret it, we guarantee** it.

* The joy of participation and being generally awesome constitutes winning
** Not an actual guarantee, but seriously, you probably won't regret it!

Serving the Subaru Community since May 18th, 1998!

Guest Message by DevFuse
 

Photo
- - - - -

Philosophical Tangent! MAF focus


  • Please log in to reply
4 replies to this topic

#1 electryc_monk

electryc_monk

    Air-ride Airehead

  • Members
  • 1,581 posts
  • Denton, Tx

Posted 30 October 2003 - 10:26 PM

What is the reasoning for placement of the MAF before the turbo?

I just had a wild hairbrained thought! And really and truthfully wonderd about the systemic problems that might or might not be of issue by placing the MAF at the mouth of the intake AFTER the turbo (and once installed also after the IC)?????


Well folks any thing I'm not realizing with respect to air fuel ratio and the like? Considering the ECU is running off the thermal reading in the air (if its a hotwire version that is) and if its getting the data from after the turbo then wouldn't the reading be more accurate then before the turbo given the temperature differential?

Could the system be simply set to WOT fore less scripting in the ROM chip for the EFI computer? And if the movement of the MAF to after the turbo (and IC) wouldn't this also allow for a interesting place for it considering the more versitility of an intake to the turbo from who knows where at this point?


Or am i just utterly forgetting a very important factor of internal combustion system dynamics?

#2 archemitis

archemitis

    guy smiley

  • Members
  • 3,554 posts
  • the big minnie

Posted 31 October 2003 - 09:51 AM

go look at some 900 horsepower japanese supras, and skilines, and all those. the reason you always see down the throat of the big fat turbo is not because they all use maP sensors(some do) but its because they moved their maF to where you are talking about.
just think, your maf thinks that the air going into it is outside templ, but by the time it gets heated up, and cooled down agian, there has to be some issues.

wouldnt a flapper door be better for that reason, it measures volume. instead of the hotwire, that just measures cooling effect.

would be cool to try. it would work for sure.
but think what would happen when your turbo started leaking oil.

#3 Nug

Nug

    Lurker/off-topic poster

  • Members
  • 1,966 posts
  • West Point

Posted 31 October 2003 - 11:03 AM

Here's something I can't figure out. Why (sometimes) are oxygen sensors located downstream of the air injection ports? I mean, you are trying to measure the amount of oxygen left in the combustion gases, right? And injecting a bunch of air before the sensor is going to add extra oxygen, right? It's gonna throw it out of whack.
Subes don't even have smog pumps, do they? So for most of you, this probably isn't an issue.
Eric

#4 rallyruss

rallyruss

    Subaru Master

  • Members
  • 1,653 posts
  • San Jose CA

Posted 31 October 2003 - 12:41 PM

Interesting thought and it might work if you are into reprograming ecu's ect.
I would not try it for a few reasons.first the air temp sensor is built into the maf and would be verry confused as to what actual inital air temp is. second the efectivness of the hot wire set up would be compromised. it calculates air flow by how much the passing air cools the heated wire. it most likely would cause an error on the lean side. not good:eh: .

to answer snot rockets question. air injection on the cars you are speaking of works on cold start up to help warm up the cat. the O2 is still sleeping untill after the air injection shuts down.

and yes older subes had pulse air injection used with carb setups.

#5 Setright

Setright

    Elite Master of the Subaru

  • Members
  • 3,176 posts
  • Denmark

Posted 01 November 2003 - 04:42 AM

Ermm, a hot wire MAF is very accurate. The flapper door system is better than nothing, but it has moving bits that wear out, and cause misreadings.

As for the location...well air only enters via the intake right? So how would the VOLUME of air change along the way? The MAF gives the ECU an accurate indication of how much air is available, and the ECU tells the injectors to do its bidding. Then, the O2 sensor is used to make sure things went as expected.

It's a very reliable system, and I wouldn't mess it. There is no need to subject the MAF to the higher air pressure aft the turbo.




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users